To meet its goal of putting Windows 10 on a billion devices within three years, Microsoft will have to turn every personal computer now running Windows 7 onto the new OS, then find even more to migrate, calculations from recent statistics show.

Microsoft staked out the ambitious plan last week at its Build developers conference. "Our goal is that within two to three years of Windows 10's release there will be one billion devices running Windows 10," said Terry Myerson, the chief of the firm's operating system group.

One billion. A big, big number.

For an idea how big, Computerworld used the user share data published by Net Applications to peg the number of PCs now running each still-supported version of Windows.

User share is a rough estimate of the percentage of the world's online users who ran a specific OS during a given month, and is tracked by Net Applications using visitor tallies to its customers' websites.

According to the California analytics vendor, Windows 7 powered 64.1% of all PCs running Windows during April. The 2009 operating system was, by far, the most popular on the planet, easily beating the second-place Windows XP, which accounted for 17.5% of all Windows PCs that month.

Together, Windows 8 and 8.1 powered 16.1% of all Windows personal computers, while the Windows Vista flop of 2007 was on just 2.1%.

Microsoft has put the number of Windows devices at approximately 1.5 billion, using that statistic several times last week when it laid out its 1-billion-in-36-months-or-less agenda.

With the 1.5 billion as a total, calculations showed that Windows 7 is on approximately 961 million machines, shy of the goal. Windows XP and Windows 8/8.1 tallied 262 million and 257 million, respectively. Meanwhile, Vista's share is about 32 million.

Microsoft could get every current Windows 7 PC and each system now running Vista onto the new Windows 10, and it would still be short a few million, even after tossing in the estimated 1.5 million systems equipped with Windows 10 today.

Most analysts have put pencils to envelopes and concluded that Microsoft will reach the billion within a three-year span, what with expected PC sales, aggressive in-place upgrading, and an uptick in Windows 10's fortune on mobile.

Perhaps. But the less-than-1-billion number for Windows 7, easily Microsoft's most successful OS since XP, makes one wonder.

Data: Net Applications

Microsoft is nothing but ambitious: Even its most popular OS, Windows 7, isn't on 1 billion PCs. Figures in millions.

This story, "Where will Microsoft find 1 billion devices for Windows 10?" was originally published by
Computerworld.